Through a number of different methods, the groundwater has been contaminated in many areas with a variety of noxious chemicals. While there are chemical methods available to remediate such pollution, a technique known as "in-situ bio-remediation" may be preferred in many cases. For example, if a population of microbial organisms capable of remediating a particular chemical pollutant either already exists in situ, or can be introduced to the subsurface zone requiring remediation, introducing excess nutrients to the microbial population to stimulate growth and biological activity can greatly enhance bio-remediation. However, before such bio-remediation can occur, a census of microbial growth must be accurately known in order to provide optimal nutrients for growth of the desired organisms.
Previously, microbial characterization typically occurred by sampling groundwater collected in a sampling well or tube at the desired location. However, it has been shown that the number of microorganisms collected free-floating in a water sample bears little or no relationship to the size of the population adhered to the subsurface strata--it is invariably smaller by a significant amount. Therefore, wells have been drilled so that soil cores can be taken, and the microorganisms therein analyzed. This method is expensive and is limited by the number of wells that can be drilled at a given location.
In groundwater, virtually all of the microbial activity is associated with biofilms--aggregations of microorganisms attached to structures as opposed to free-floating. For example, if the water collected in wells is used, it is estimated that approximately 100 liters of groundwater must be filtered to provide the same biomass that might be available from an equivalent volume of a single core sample.
The use of in-situ coupons is contrary to standard bioremediation monitoring methods that are directed at free-floating microorganisms. Current methods for the use of RNA probes require that over 500 liters of contaminated groundwater be pumped to the surface to recover approximately 0.5 grams of biomass for analysis. As a result, the 500 liters of groundwater, per sample, must be disposed of as hazardous waste. Additionally, the microorganisms that are recovered represent only the population in the ground water, not the quantity actually in the strata that are responsible for the bulk of the bioremediation.
In addition, there is a need for a system to measure the accumulation rate of the in-situ biofilm formation during the active bioremediation process, and to determine the effects of in-situ biomass transport processes such as cellular attachment and detachment.